Activated dolomite phosphate rock fertilizers to reduce leaching of phosphorus and trace metals as compared to superphosphate.

Use of water-soluble phosphorus (P) fertilizers such as superphosphates (SP) has been increasingly concerned due to the loss of P and trace metals such as cadmium (Cd) into the environment. Activated phosphate rock holds promising as an alternate due to non-destructive and slow release nature. The objective of this study was to assess the leaching potential of P and trace metals from newly developed activated dolomite phosphate rock (HA-DPR and SLS-DPR), as compared to water-soluble fertilizers, including superphosphate (SP), diammonium phosphate (DAP) and original dolomite phosphate rock (DPR). Two representative agricultural soils (Alfisol and Spodosol soil) were sampled at the 0-20 cm depth from two farms for the column leaching experiments. Seven leachings were conducted at day 1, 3, 7, 14, 21, 28, and 56, respectively, and a total of 1050 mL of deionized water (equivalent to half year's rainfall in the Indian River area) was applied for leaching. Leachates were collected from each leaching event and analyzed for water-soluble P and metals. Activated DPR application led to an increase in soil pH by 1.4-1.7 units, whereas SP resulted in a decrease in soil pH by 0.4-1.6 units. P leaching from activated DPR were 33-61 times less than that from SP or DAP. HA-DPR and SLS-DPR treatments reduced cumulative trace metals in leachate by 1.3-12.3 times for the Alfisol soil, and 1.4 to 8.4 times for the Spodosol soil, respectively. These results indicate that activated DPR fertilizers are more environmentally friendly than water-soluble fertilizers.

Wang X ，Xiong J ，He Z 《-》

Dolomite phosphate rock (DPR) application in acidic sandy soil in reducing leaching of phosphorus and heavy metals-a column leaching study.

Yang Y ，He Z ，Yang X ，Stoffella PJ ... -  《-》

Use of dolomite phosphate rock (DPR) fertilizers to reduce phosphorus leaching from sandy soil.

Chen GC ，He ZL ，Stoffella PJ ，Yang XE ，Yu S ，Calvert D ... -  《ENVIRONMENTAL POLLUTION》

Leaching potential of heavy metals (Cd, Ni, Pb, Cu and Zn) from acidic sandy soil amended with dolomite phosphate rock (DPR) fertilizers.

Chen GC ，He ZL ，Stoffella PJ ，Yang XE ，Yu S ，Yang JY ，Calvert DV ... -  《JOURNAL OF TRACE ELEMENTS IN MEDICINE AND BIOLOGY》

Release of Heavy Metals from Dolomite Phosphate Rock after Activation with Organic Agent.

As high-grade phosphate reserves begin to diminish worldwide, low-grade phosphate rock such as that containing dolomite [CaMg(CO)] needs to be explored as a potential fertilizer. Activation of dolomite phosphate rock with humic acid substantially increased P availability by chelating Ca and Mg. However, the release potential of heavy metals during the activation process should be evaluated. In this study, an orthogonal experiment was designed to investigate the effects of major activating factors on the release of Cd, Cr, Cu, Mn, Ni, Pb, and Zn in activated fertilizers using a batch-equilibrium technique. The release potential of heavy metals from activated fertilizers was further compared with single superphosphate fertilizers made from the same dolomite phosphate rock. The activation process increased water-soluble Cr, Ni, and Zn by 39.8 to 65.7, 26.5 to 35.6, and 6.9 to 14.6 times, respectively, as compared with the original dolomite phosphate rocks, but there was a decrease in water-soluble Cd, Mn, Ni, Pb, and Zn by 1.4 to 5.4, 5.4 to 8.6, 2.3 to 3.7, 0.7 to 2.8, and 2.6 to 5.0 times, respectively, as compared with single superphosphate fertilizers. The release of heavy metals was affected by activating factors including dolomite phosphate rock type, particle size, humic acid dosage, and moisture content. Similar results were obtained with Mehlich-3 extraction, but levels of Mehlich-3-extractable heavy metals were less in activated fertilizers than in the original dolomite phosphate rocks, except Cu. These results indicate that activated fertilizers contain less bioavailable heavy metals than single superphosphate fertilizers and, therefore, are more environmentally friendly for application in agriculture.

Yu Y ，Xiong J ，Liu R ，He Z ... -  《-》